Want to verify if water pump impellars have failed, (no heat and temp bottoms out at hwy speed) not sure how to check this system, water doesn't appear to circulate like a normal system due to the overflow tank tie in. Doesn't have the normal in/out hoses should there be a visible flow with the cap off the tank? Tank has 2 small overflow feeders on top and a primary at the bottom feeding the radiator.
You can remove the upper radiator hose, put something on the ground to catch the coolant and start the engine to see if it's circulating. You will have to wait until the thermostat opens and keep feeding water to the radiator to be sure it doesn't run out. Other than that, removing the pump is the only way to find out. This does happen to fords more than any other make.